Ventilating plants



June 1959 R. R. HUITSON 2,891,717

- VVENTILATINGV PLANTS Filed July 30. 1956 United States Patent y InA'mvG PLANTS Robert Ross Huitson, Rugby, England, assignor to The British Thomson-Houston Company Limited, London, England, a'Brilish company This invention relates to ventilating plants particularly of a kind required to deliver air at a specified high pressure during some periods, and a substantially lower pressure during intervening periods.

In certain applications, such as for mine ventilation, it is necessary to deliver air at high pressure only during the periods when men are working, while a lesser ventilation at lower pressure is desirable at other times. It may well be that the lesser ventilation at lower pressure is required for sixteen hours, and the higher pressure for only eight hours each day. Up to now it has been customary in such circumstancees to provide continuously air at the high pressure, although it has also been tentatively suggested that two compressors driven by separate machines could be employed so that a machine for providing the lesser ventilation would operate continuously, and another machine would operate only to afiord full strength ventilation when men are working in the mine.

One object of the present invention therefore is to provide an improved arrangement which is more compact, and more economical both in manufacture and service.

Another object is to employ a single compressor set or unit with means permitting the selection of alternative discharge pressures. As the power required to drive a compressor corresponds to the pressure at which air is delivered, a useful economy in the operating costs can be achieved. A further advantage is that the serviceable life of the driving motor, which now operates at considerably less than full load torque during the low pressure periods, is appreciably extended.

Generally the invention can be embodied in a ventilating plant comprising an electric motor driving low pressure and high pressure compressors in series flow arrangement, a diverter valve means disposed between the high and low pressure compressors and a pressure output supply line connected both to the high pressure compressor discharge and the outlet of the diverter valve means, so that in accordance with the position of said diverter valve means high pressure or low pressure air is discharged into the supply line.

A second valve means is arranged at the discharge side of the high pressure compressor to connect it selectively to the pressure output supply line or .to the outer atmosphere when high pressure air or low pressure air respectively has to be discharged to the pressure output supply line. In addition third valve means of the one-way type are arranged for allowing air flow in the direction towards the said supply line only and yet another one-way valve means can be arranged at the inlet of the high pressure compressor to connect it to the surrounding atmosphere when the internal pressure of said compressor falls :below the external pressure.

It will be appreciated that the power required to drive the high pressure compressor is very small when both its inlet and outlet are connected to atmosphere. Thus a 25% reduction in input power can be readily efiected.

An exemplary embodiment of the invention is shown Patented J ne 23, 1959' 2 v very diagrammatically in the single figure of the. accompanying drawing to illustrate clearly the principle and spirit of the present invention without distracting details.

A machine set according to the invention is here illus, trated to comprise an electric motor 1, a speed increasing gearbox 2, a low pressure compressor 3, and ahigh pressure compressor 4. A pressure output supply line10 for directing high'or low pressure airinto a utilisation circuit is connected through branch lines'll, '12'respec5 tively to the outlet of a diverter valve 5 arranged between the two compressors, and to the discharge' side of the high' pressure compressor, which-is shown'at theright hand end of the figure and is adapted to communicate if required with the atmosphere through a second valve means such as a changeover valve 6. Non-return or one-way valves 7, 8 and 9 are diagrammatically indicated at the inlet side of the compressor 4, and in the branches 8, 9, the oneway flow direction through the valves as indicated by arrows being towards the inlet of compressor 4 (for valve 7) and towards the pressure output supply line 10 (for valves 8, 9).

The operation is as follows: During the period when high pressure is required the two compressors are connected in series, the air intake being at A, the output at B, and the diverter valve 5 being in the position shown in the drawing to direct the output of the low pressure compressor 3 into the high pressure compressor 4, as required. Preferably the changeover valve 6 is mechanically coupled to the diverter valve 5 to close when 5 opens to the compressor 4, and to open for connecting the high pressure side of compressor 4, to the atmosphere when valve 5 opens to the branch line 11. Non-return valve 7 opens to atmosphere when the internal pressure at the intake side of compressor 4 falls below atmospheric pressure during opening of the diverter valve 6 at low pressure air supply operation, and allows the admission of a limited quantity of air to permit the high pressure compressor to operate at no load.

Suitable couplings 14, 15 are provided for transmitting driving power from the gear box 2 to the shafts of the compressors 3, 4, such couplings being preferably of a type, such as hydraulic or magnetic, suitable for rapid decoupling, so that the high pressure compressor can be de-coupled instantly and need not run idle during periods of low pressure air supply.

In some instances, it is desirable that the air be supplied at a relatively lower temperature than that in the mine or other enclosure into which it is blown. This can conveniently be provided by arranging a suitable cooler 16 in the ducting 13 between the lower pressure compressor stage 3 and the diverter valve 5.

Many variations of the present invention will be obvious to one skilled in the art. For instance, a common housing may be used for the two compressor stages and diverter valve 5 may then be connected at a point of the housing between the two compressors. Such an obvious variation, and all other modifications within the spirit and scope of this invention, are intended to be included in the definition of the invention by the appended claims.

What I claim is:

l. A ventilating plant comprising a first compressor and a second compressor, a common driving means coupled to both of said compressors, means forming a common delivery opening for said compressors, both of said compressors having outlets and individual branch ducts connecting said outlets to said delivery opening, inlets for each compressor, means forming a passage for directing fluid flow to said inlet of said second compressor, means including a two-position diverter valve between said first compressor outlet and its branch duct and said passage for connecting in its first position said first comresser outlet to said first compressor branch duct and in its second position said first compressor outlet to said second compressor inlet, a two-position change-over valve in said second compressor branch duct for directing respectively in its first and second positions fluid flow from said second compressor outlet to atmosphere and to said common delivery opening, an automatic non-return valve at said second compressor inlet providing for the intake of atmospheric air to said second compressor when said diverter and change-over valves are each in their first positions, and an automatic non-return valve in said second compressor branch duct for directing fluid flow from said second compressor outlet to said common delivery opening wher said diverter and changeover valves are each in their second positions.

2. A plant as claimed in claim 1, wherein means a mechanically couple together said diverter valve and changeover valve for simultaneous operation.

3. A plant as claimed in claim 1, including a nonreturn valve arranged in said first compressor branch duct for providing for fluid flow from said diverter valve to said common delivery opening.

4. A plant as claimed in claim 1, wherein an intercooler is arranged between the first compressor outlet and diverter valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,391,486 Smith Dec. 25, 1945 2,491,482 Dolza et a1 Dec. 20, 1949 2,648,490 Messinger Aug. 11, 1953 

